Why the alignemt to 4 bytes is necessary in jffs2_commit_write function

[David Woodhouse]

On Wed, 2007-07-11 at 20:25 +0400, akorolev wrote:
> If I properly understand the aligned_start is not related to offset of
> the fragment it is just offset within the file.  (Frag offset is
> aligned) File offset is not necessary to keep aligned - so why not to
> kick off it. (I tried and didn't find anything wrong in tests).

Consider:
	while (1)
		write(fd, "x", 1);

This is fairly much worst-case behaviour for JFFS2, and you end up with
a _large_ number of data nodes. One thing we've done to improve
behaviour in this situation is rewrite the entire page when we write the
last byte in a page -- but that doesn't fix _all_ cases.

Since data nodes _are_ aligned to 4 bytes, it doesn't hurt us at all to
write a full 4 bytes instead of only 1 byte. So you'll have a maximum of
1024 data nodes for a given 4KiB page even if you don't manage to
trigger the code which rewrites the page.

-- 
dwmw2